1. Field of the Invention
The present invention concerns booths for drying and curing coating composition. More particularly, the present invention concerns such booths which introduce heated and/or cooled turbulent air to the interior of the booth to dry and cure articles therein. Even more particularly, the present invention pertains to such booths which introduce humid and/or dry turbulent air to the interior of the booth to dry and/or cure articles therein.
2. Description of the Prior Art
As is known to those skilled in the art to which the present invention pertains, many industries are being switched to water-based paints from solvent-based paints because of the volatile organic chemicals (VOCs) in the solvents. The elimination of VOCs for environmental purposes is well documented. However, the utilization of water-based paints creates issues ordinarily not encountered with solvent-based paints.
For example, since water evaporates much slower than solvents, water-based coating compositions dry at a much slower rate than coating compositions which are solvent-based in most any given environment. Because drying systems are expensive, quick drying cycles are vital for manufacturing processes in which articles of manufacture have been painted or coated with a composition.
In addition, there now also exists low-VOC aqueous coatings which are water activated. These types of coatings are known generally as “moisture cure” polyurethanes, or otherwise as Waterborne Chemical Agent Resistant Coatings (CARC). As understood, these coatings comprise a two-part composition, such as a urethane, which requires the presence of water in order to properly cure. To properly coat articles of manufacture with these coatings, water must first be removed to complete the drying process, and then again added in specific amounts to properly cure the coating.
These paints are advantageous because they have a low-VOC content, high durability, a long wet edge that eliminates dry spray, and an excellent film build which results in up to 30% less coating resulting in material savings. In addition, they have less odor, can be electrostatically applied, and can be non-flammable. Specific examples of these coatings include those sold under designation “MIL-DTL-64159 Type II-Waterborne” by Sherwin-Williams.
However, as discussed above, it is only feasible to use these paints if the drying cycles can be reduced to acceptable durations. Although traditional paint-drying booths are adept at circulating heated air within the booth to dry the paint, the booths known in the prior art cannot create the proper environment by reintroducing water into the booth as required by these water-activated paints.
As confirmed in laboratory testing performed by the Iowa Waste Production Center in April 2005, Waterborne CARC paints require at least 6½ hours to obtain a moderate level of dryness in favorable drying conditions. In order to obtain a “scratch resistant” level of dryness, these paints require over 24 hours in a favorable drying environment.
As will be described hereinbelow, the present invention provides a drying booth which can quickly alter the environment within the booth with respect to both the temperature and humidity to substantially reduce drying durations known in the prior art. Even more so, the present invention can properly dry and cure water-activated paints in a time which dramatically exceeds the capabilities of the prior art.